<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
    <button class="sky">测试</button>
</body>
<script src="../jquery-1.12.4.min.js"></script>
<script>
    // 【知识点】console.count能够打印函数内部执行次数
    $(function() {
        $(".sky").on("mouseenter mouseleave", function() {
            var a = console.count("计数测试")
            debugger
        })
    })
</script>

</html>